Liquid crystal display device having a light path changing means having a porous film with a plurality of pores

ABSTRACT

Disclosed is a liquid crystal display device capable of improving a viewing angle thereof while reducing a gray scale inversion. The liquid crystal display device has a porous film aligned on a liquid crystal display panel and having a plurality of pores. The porous film has sidewalls defined by the pores and reflecting a part of light exited from the liquid crystal display panel. That is, the sidewalls reflect a first group of light, which has relatively higher luminance by passing through a short axis of liquid crystal, towards a second group of light having a relatively lower luminance by passing through a long axis of liquid crystal. Accordingly, the viewing angle of the liquid crystal display device is expanded and the gray scale inversion is reduced.

TECHNICAL FIELD

The present invention relates to a liquid crystal display device, andmore particularly to a liquid crystal display device capable ofimproving a viewing angle thereof and simultaneously capable of reducinga gray scale inversion.

BACKGROUND ART

Generally, a liquid crystal display (LCD) device includes a firstsubstrate having a first electrode, a second substrate having a secondelectrode opposite to the first electrode, and liquid crystal disposedbetween the first and second substrates. The liquid crystal displaydevice changes an alignment of liquid crystal by applying electric fieldto both the first and second electrodes to adjust quantity of lightpassing through liquid crystal, thereby displaying various images.

Twisted nematic (hereinafter, referred to TN) liquid crystal, in which along axis of liquid crystal is continuously twisted from the firstelectrode towards the second electrode at a right angle, is mainly usedin the liquid crystal display device.

Although TN liquid crystal is irregularly aligned, it has apredetermined alignment order with respect to an axis of liquid crystal.TN liquid crystal has different physical properties in a long axisdirection and a short axis direction thereof, respectively. That is, TNliquid crystal has optically anisotropic characteristic.

Hereinafter, a conventional TN-type liquid crystal display device, whichdisplays images by using above-mentioned TN liquid crystal, will bedescribed.

FIG. 1 is an exploded perspective view of a conventional TN-type liquidcrystal display device 400.

Referring to FIG. 1, the TN-type liquid crystal display device 400includes a backlight unit 200 for generating light, a display unit 100for receiving light from the backlight unit 200 to display images, amold frame 250 for accommodating the backlight unit 200 and the displayunit 100, and a chassis 300 therein.

The display unit 100 has a liquid crystal display panel 110 fordisplaying images, printed circuit boards 120 and 140 for supplying adriving signal and an image data signal to the liquid crystal displaypanel 110, and tape carrier packages (hereinafter, referred to TCP) 130and 150 disposed between the liquid crystal display panel 110 and theprinted circuit boards 120 and 140 in order to electrically connect theprinted circuit boards 120 and 140 to the liquid crystal display panel110.

The liquid crystal display panel 110 includes a thin film transistorsubstrate (hereinafter, referred to TFT substrate) 112 having thin filmtransistors (TFTs, not shown) and pixel electrodes (not shown), a colorfilter substrate 114 opposite to the TFT substrate 112 and having colorfilters and common electrode, and liquid crystal (not shown) disposedbetween the TFT substrate 112 and the color filter substrate 114.

In detail, the TFT substrate 112 includes a plurality of data lines (notshown) extended in a row direction thereof and a plurality of gate lines(not shown) extended in a column direction thereof. In addition, aplurality of TFTs are arranged on the TFT substrate 112 in a matrixshape. That is, source electrodes of the TFTs are connected to the datalines, and gate electrodes of the TFTs are connected to the gate lines.Drain electrodes of the TFTs are connected to the pixel electrodes.

One end of each data line is coupled to a data-side TCP 130 equippedwith a data driver chip, and one end of each gate line is coupled to thegate-side TCP 150 equipped with a gate driver chip.

The data-side TCP 130 is connected to a data-side printed circuit board120 so as to timely apply image data signal inputted from the data-sideprinted circuit board 120 to the data lines. In addition, the gate-sideTCP 150 is connected to the gate-side printed circuit board 140 so as toapply a gate driving signal inputted from the gate-side printed circuitboard 140 to the gate lines.

On the other hand, the backlight unit 200 includes a light source 210for generating first light, and a light guiding plate 220 for guidingthe first light towards the liquid crystal display panel 110. The lightsource 210 includes a lamp (lamps) 211 generating the first light and alamp reflection plate 213 covering one side of the lamp (lamps) 211 toreflect the first light towards the light guiding plate 220.

The light guiding plate 220 is disposed at the other side of the lamp211 and includes an incident surface through which the first light isincident, a reflection surface for guiding the first light towards theliquid crystal display panel 110, and an exiting surface for outputtingthe first light towards the liquid crystal display panel 110.

In addition, the backlight unit 200 includes a reflection plate 240 anda plurality of optical films 230. The reflection plate 240 is disposedbelow the light guiding plate 220 and reflects light leaked from thelight guiding plate 220 towards the liquid crystal display panel 110.The plurality of optical films 230 allows the light outputted from thelight guiding plate 220 to have uniformly distributed luminance.

Since the conventional TN type liquid crystal display device 400 havingthe above structure uses the TN crystal having optical-anisotropiccharacteristic, a color and a contrast ratio (C/R) of the images varydepending on viewing angles. Therefore, the conventional TN type liquidcrystal display device 400 may limit a range of viewing angles forallowing a user to precisely recognize information displayed in a screenof the conventional TN type liquid crystal display device 400.

Although it is not shown in the figures, the conventional liquid crystaldisplay device includes a compensating film (wide view film) having adiscotic layer so as to solve the above problem. However, although thecompensating film can improve the viewing angle, gray scale inversionoccurs when the viewing angle exceeds a predetermined level.

That is, a normal gray level can be found when a user look at the liquidcrystal display panel 110 at a front thereof However, an abnormal graylevel is found when a viewing position of the user is changed upward ordownward the front of the liquid crystal display panel 110. When theliquid crystal display panel 110 is viewed with a viewing angleexceeding a critical viewing angle, a white gray scale is erroneouslyrecognized as a black gray scale, or the black gray scale is erroneouslyrecognized as the while gray scale, called “gray scale inversion”.

DISCLOSURE OF THE INVENTION

The present invention has been made to solve the above problems of therelated art, therefore, it is an object of the present invention is toprovide a liquid crystal display device capable of improving a viewingangle thereof while reducing a gray scale inversion.

In order to achieve the above object of the present invention, accordingto one aspect of the present invention, there is provided a liquidcrystal display device comprising: a liquid crystal display panel forreceiving a first light, and for radiating a second light having animage information, the liquid crystal display panel including: i) afirst substrate on which a plurality of pixels having a first electrodeis formed, ii) a second substrate on which a second electrode oppositeto the first electrode is formed, and iii) a liquid crystal layer,disposed between the first and second substrate, which is aligned by anelectric field applied between the first and second electrodes; and alight path changing means disposed on the liquid crystal display panel,the light path changing means including a reflection surface, thereflection surface reflecting a part of the second light and outputtinga third light having a compensated luminance, and the reflection surfacebeing extended in a first direction perpendicular to an upper surface ofthe liquid crystal display panel.

In one aspect of the invention, there is provided a liquid crystaldisplay device comprising: a liquid crystal display panel for receivinga first light, and for radiating a second light having an imageinformation, the liquid crystal display panel including: i) a firstsubstrate on which a plurality of pixels having a first electrode isformed, ii) a second substrate on which a second electrode opposite tothe first electrode is formed, and iii) a liquid crystal layer, disposedbetween the first and second substrate, which is aligned by an electricfield applied between the first and second electrodes; and a polarizingplate disposed on the liquid crystal display panel, the polarizing plateincluding: i) a polarizing layer for polarizing the second light, andii) a light path changing layer including a reflection surface, thereflection surface for reflecting a part of the second light andoutputting a third light having a compensated luminance, the reflectionsurface extended in a first direction perpendicular to an upper surfaceof the liquid crystal display panel.

In further aspect, there is provided a liquid crystal display devicecomprising: a liquid crystal display panel for receiving a first light,and for radiating a second light having an image information, the liquidcrystal display panel including: i) a first substrate on which aplurality of pixels having a first electrode is formed, ii) a secondsubstrate on which a second electrode opposite to the first electrode isformed, and iii) a nematic liquid crystal, disposed between the firstand second substrate, which is aligned by an electric field appliedbetween the first and second electrodes; and a light path changing meansdisposed on the liquid crystal display panel, the light path changingmeans including a reflection surface, the reflection surface reflectinga part of a first group of the second light towards a second group ofthe second light, the first group of the second light passing throughthe nematic liquid crystal in a parallel direction with regard to afirst axis of the nematic liquid crystal tilted at a predetermined angleby the electric field, the second group of the second light passingthrough the nematic liquid crystal in a parallel direction with regardto a second axis of nematic liquid crystal, and the second axis beingperpendicular to the first axis of nematic liquid crystal.

In further aspect, there is provided a liquid crystal display devicecomprising: a liquid crystal display panel for receiving a first light,and for radiating a second light having an image information, the liquidcrystal display panel including: i) a first substrate on which aplurality of pixels having a first electrode is formed, ii) a secondsubstrate on which a second electrode opposite to the first electrode isformed, and iii) a nematic liquid crystal, disposed between the firstand second substrate, which is aligned by an electric field appliedbetween the first and second electrodes; and a polarizing plate disposedon the liquid crystal display panel, the polarizing plate including: i)a polarizing layer for polarizing the second light, and ii) a light pathchanging layer including a reflection surface, the reflection surfacehaving a plurality of pores and inner sidewalls adjacent to each of thepores, the inner sidewalls reflecting a part of a first group of thesecond light towards a second group of the second light, the first groupof the second light passing through the nematic liquid crystal in aparallel direction with regard to a first axis of the nematic liquidcrystal tilted at a predetermined angle by the electric field, thesecond group of the second light passing through the nematic liquidcrystal in a parallel direction with regard to a second axis of nematicliquid crystal, and the second axis being perpendicular to the firstaxis of nematic liquid crystal.

In further aspect, there is provided a liquid crystal display devicecomprising: a lower substrate including: i) a plurality of switchingdevices arranged in a matrix shape on a first substrate, ii) a firstelectrode electrically coupled to the switching devices, and iii) afirst alignment layer deposited on the first substrate and having afirst rubbing pattern extended in a first direction; an upper substrateincluding: i) a color filter formed on a second substrate, ii) a secondelectrode formed on the color filter, and iii) a second alignment layerdeposited on the second electrode and having a second rubbing patternextended in a second direction; a liquid crystal layer disposed betweenthe upper and lower substrates; and a light path changing meansincluding a plurality of pores and sidewalls being defined by the pores,the light path changing means disposed on the upper substrate andreflecting a part of a first light to output a second light having acompensated luminance distribution, the first light exited from theupper substrate and being incident into sidewalls of the light pathchanging means.

In further aspect, there is provided a liquid crystal display devicecomprising: a lower substrate including: i) a plurality of switchingdevices arranged in a matrix shape on a first substrate, ii) a firstelectrode electrically coupled to the switching devices, and iii) afirst alignment layer deposited on the first substrate and having afirst rubbing pattern extended in a first direction; an upper substrateincluding: i) a color filter formed on a second substrate, ii) a secondelectrode formed on the color filter, and iii) a second alignment layerdeposited on the second electrode and having a second rubbing patternextended in a second direction; a liquid crystal layer disposed betweenthe upper and lower substrates; a first polarizing means, disposed on alower surface of the lower substrate, for polarizing a first lightincident into the lower substrate; and a second polarizing means,disposed on the upper substrate, for polarizing a second light exitedfrom the upper substrate, and for reflecting a part of second light tooutput a third light having a compensated luminance.

According to the liquid crystal display device of the present invention,the porous film includes sidewalls defined by a plurality of pores andreflects a first group of light, which is exited from the liquid crystaldisplay panel and passes through a short axis of liquid crystal, towardsa second group of light passing through a long axis of liquid crystal.Therefore, a gray scale inversion can be reduced and the viewing angleof the liquid crystal display device can be expanded.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object, and other features and advantages of the presentinvention will become more apparent by describing preferred embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is an exploded perspective view showing a conventional TN-typeliquid crystal display device;

FIG. 2 is an exploded perspective view showing a liquid crystal displaydevice according to one exemplary embodiment of the present invention;

FIG. 3 is a sectional view showing a structure of a liquid crystaldisplay device shown in FIG. 2;

FIGS. 4 and 5 are views showing a light path to be changed by a firstporous film;

FIGS. 6A to 6E are views showing a plurality of pores formed in a firstporous film;

FIGS. 7A and 7B are views showing a second porous film according toanother exemplary embodiment of the present invention;

FIGS. 8A and 8B are views showing a third porous film according to stillanother exemplary embodiment of the present invention;

FIGS. 9 and 10 are views showing a structure of a polarizing plate of aliquid crystal display device according to an exemplary secondembodiment of the present invention;

FIGS. 11A to 11C are graphs showing luminance variation according toviewing angles obtained by using comparative sample 1;

FIGS. 12A to 12C are graphs showing luminance variation according toviewing angles obtained by using sample 1;

FIGS. 13A to 13C are graphs showing luminance variation according toviewing angles obtained by using sample 2;

FIG. 14 is an exploded perspective view showing a liquid crystal displaydevice according to an exemplary third embodiment of the presentinvention;

FIG. 15 is a sectional view showing a liquid crystal display deviceshown in FIG. 14;

FIG. 16 is a schematic view showing a display unit shown in FIG. 14;

FIG. 17 is a schematic view showing a viewing angle characteristicaccording to rubbing directions of first and second alignment layersshown in FIG. 16;

FIG. 18 is a schematic view showing a light path to be changed by aporous film shown in FIG. 14;

FIGS. 19 and 21 are sectional views showing a liquid crystal displaydevice according to the exemplary fourth embodiment of the presentinvention;

FIG. 20 is a perspective view showing a display unit shown in FIG. 19;

FIGS. 22A to 22C are graphs showing simulation results obtained throughexperiment 1 according to the present invention;

FIGS. 23A to 23C are graphs showing simulation results obtained throughexperiment 2 according to the present invention;

FIGS. 24A to 24C are graphs showing simulation results obtained throughcomparative experiment 1; and

FIGS. 25A to 25C are graphs showing simulation results obtained throughcomparative experiment 2.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. The samereference numerals are used to refer the same elements.

FIG. 2 is an exploded perspective view showing a liquid crystal displaydevice 1000 according to an exemplary first embodiment of the presentinvention and FIG. 3 is a sectional view of the liquid crystal displaydevice 1000 shown in FIG. 2.

Referring to FIGS. 2 and 3, the liquid crystal display device 1000includes a backlight unit 600 for generating first light, and a displayunit 500. The display unit 500 receives the first light and radiatessecond light having image information, to thereby display images.

The display unit 500 has a liquid crystal display panel 510 fordisplaying images, printed circuit boards 520 and 540 for supplyingdriving signals and image data signals to the liquid crystal displaypanel 510, and TCPs 530 and 550 disposed between the liquid crystaldisplay panel 510 and the printed circuit boards 520 and 540 so as toelectrically connect printed circuit boards 520 and 540 to the liquidcrystal display panel 510.

The liquid crystal display panel 510 includes a TFT substrate 512 havingTFTs and pixel electrodes, a color filter substrate 514 facing the TFTsubstrate 512 and having color filters and common electrode, and liquidcrystal (not shown) disposed between the TFT substrate 512 and the colorfilter substrate 514.

The TN liquid crystal, in which a long axis of liquid crystal iscontinuously twisted at a right angle from the pixel electrode towardsthe common electrode, is mainly used in the liquid crystal displaydevice.

The TFT substrate 512 includes a plurality of data lines (not shown)extended in a row direction thereof and a plurality of gate lines (notshown) extended in a column direction thereof. In addition, a pluralityof TFTs is arranged on the TFT substrate 512 in a matrix shape. Sourceelectrodes of the TFTs are connected to the data lines, and gateelectrodes of the TFTs are connected to the gate lines. Drain electrodesof the TFTs are connected to the pixel electrodes.

One end of each data line is coupled to the data-side TCP 530 equippedwith a data driver chip, and one end of each gate line is coupled to thegate-side TCP 550 equipped with a gate driver chip.

The data-side TCP 530 is connected to the data-side printed circuitboard 520 so as to timely apply image data signal inputted from thedata-side printed circuit board 520 to the data lines. In addition, thegate-side TCP 550 is connected to the gate-side printed circuit board540 so as to apply gate driving signal inputted from the gate-sideprinted circuit board 540 to the gate lines.

A first porous film 560 is disposed on the liquid crystal display panel510. A dimension of the first porous film 560 corresponds to that of theliquid crystal lo display panel 510, and the first porous film 560 has aplurality of pores. Inner sidewalls of the first porous film 560 definedby the plurality of pores change a path of the second light, which isexited from the liquid crystal display panel 510 and includes imageinformation, to output a third light providing an expanded viewingangle.

The first porous film 560 includes a first incident surface 561discontinuously extended in a first direction D1, a first exitingsurface 562 opposite to the first incident surface 561, and sidewalls563 connecting the first incident surface 561 to the first exitingsurface 562 and extended in a second direction D2. Hereinafter, thesidewalls 563 are defined as “inner sidewalls” defined by the pluralityof pores 565. The first porous film 560 is comprised of a high polymerresin, such as a transparent acryl resin, having a predeterminedrefractive index.

Although it is not illustrated in the figures, the pores 565 can beformed at the first porous film 560 through various well-knownprocesses. For example, the pores 565 can be formed at the first porousfilm 560 by using silica particles, by irradiating laser beam into ahigh polymer film, or by performing, a photolithography process. Thesetechniques for fabricating the first porous film 560 are well-known inthe art, and will not be further described below.

In addition, the backlight unit 600 includes a light source 610 forgenerating first light and a light guiding plate 620 for guiding thefirst light towards the liquid crystal display panel 510.

The light source 610 includes a lamp (lamps) 611 for generating thefirst light and a lamp reflection plate 613 for covering one side of thelamp 611 to reflect the first light towards the light guiding plate 620.

The light guiding plate 620 is disposed at the other side of the lamp(s)611, is a hexahedron-shaped plate, and includes an incident surface forreceiving the first light, a reflection surface for guiding first lighttowards the liquid crystal display panel 510, and an exiting surface foroutputting the first light towards the liquid crystal display panel 510.Accordingly, the light guiding plate 620 guides the first light towardsthe liquid crystal display panel 510.

In addition, the backlight unit 600 includes a reflection plate 640disposed below the light guiding plate 620 to reflect light leaked fromthe light guiding plate 620 towards the liquid crystal display panel510, and a plurality of optical sheets 630 for allowing the lightoutputted from the light guiding plate 620 to have luminance uniformlydistributed.

The backlight unit 600 and the display unit 500 having the abovestructure are sequentially accommodated in a receiving space of a moldframe 700. Then, the backlight unit 600 and the display unit 500 arefixed to the mold frame 700 by a chassis 800 facing the mold frame 700.

FIGS. 4 and 5 are views showing a light path to be changed by the firstporous film.

Referring to FIG. 4, the liquid crystal display panel 510 includes thefirst porous film 560. The first porous film 560 partially changes thepath of the second light exited from the liquid crystal panel 510, andoutputs third light providing an expanded viewing angle.

The liquid crystal display panel 510 includes the TFT substrate 512comprised of a plurality of pixels 513, the color filter substrate 514having color filters 514 a and common electrode 514 b, and liquidcrystal 515 disposed between the TFT substrate 512 and the color filtersubstrate 514. Each pixel 513 has a TFT 512 a and a pixel electrode 512b.

When voltage is provided between the pixel electrode 512 b and thecommon electrode 514 b, an electric field is formed between the pixelelectrode 512 b and the common electrode 514 b. Accordingly, analignment angle of liquid crystal 515 varies, so that quantity of firstlight L1 incident into the liquid crystal display panel 510 is adjusteddepending on the alignment angle. Therefore, a predetermined quantity ofsecond light L2 is outputted.

The second light L2 exits from the liquid crystal display panel 510, andis incident into the first porous film 560. A first part of the secondlight L2 is incident into the incident surface 651 of the first porousfilm 560, a second part of second light L2 is incident into thesidewalls 563 of the first porous film 560, and the remaining of thesecond light L2 is incident into the pores 565 of the first porous film560. The sidewalls 565 of the first porous film 560 reflect a first anda second group of light (L21 and L22) of the second light L2, which areincident into the sidewalls 565 of the first porous film 560 and have afirst incident angle larger than a critical angle of the first porousfilm 560.

Although it is not illustrated in the figures, the first porous film 560refracts a third group of light of the second light L2, which isincident into the incident surface 561 of the first porous film 560 andhas a second incident angle smaller than the critical angle of the firstporous film 560, to thereby output fourth light having an exiting angledifferent from the second incident angle. In addition, a remained fourthgroup of light L24, excepting the first, the second and the third groupof light, of the second light L2 is outputted through the pores 565.

A size (w1) of the pores 565 formed in the first porous film 560 ispreferably smaller than a size (w2) of the pixel 513 formed on the TFTsubstrate 512. In addition, a thickness (d) of the first porous film 560is in a range of about 5 to about 10 μm. It is preferred that thethickness (d) of the first porous film 560 is wide enough such that asufficient quantity of light of the second light L2, which is exitedfrom the liquid crystal display panel 510, may be incident into thesidewalls 565 of the first porous film 560. However, it is required tolimit the thickness (d) of the first porous film 510 so as to provide aliquid crystal display device with a slim structure.

Referring to FIGS. 4 and 5, when voltage is provided between the pixelelectrode 512 b of the TFT substrate 512 and the common electrode 514 bof the color filter substrate 514, an electric field is formed betweenthe pixel electrode 512 b and the common electrode 514 b, and a longaxis of liquid crystal 515 is tilted at a predetermined angle withrespect to the first direction D1. When the first light L1 is providedto the liquid crystal display panel 510, the quantity of first light L1incident into the liquid crystal display panel 510 is adjusted by thetilted liquid crystal, to thereby output the second light L2 includingimage information.

As shown in FIG. 5, if the liquid crystal 515 is tilted toward the firstdirection D1, the first group of light L21 passed through the long axisof liquid crystal 515 is reflected by a first sidewall 563 a and isexited from the first sidewall 563 a, and the second group of light L22passed through a short axis of liquid crystal 515 is reflected by asecond sidewall 563 b opposite to the first sidewall 563 a and is exitedfrom the second sidewall 563.

In addition, front-side light L24-f of the fourth group of light L24,which penetrates though the pores 565, passes through the liquid crystal515 in a direction parallel to the first direction D1 to be exited fromthe liquid crystal 515. Right-side light L24-r of the fourth group oflight L24 passes through liquid crystal 515 in a direction between thesecond direction D2 and a long-axis direction to be exited from theliquid crystal 515, and left-side light L24-l of the fourth group oflight L24 is passes through the liquid crystal 515 in a directionbetween the second direction D2 and a short-axis direction to be exitedfrom the liquid crystal 515.

Since the first group of light L21 passes through the long axis ofliquid crystal 515, the first group of light L21 loses a relativelylarge quantity of light while passing through liquid crystal 515compared with the second group of light L22. On the contrary, since thesecond group of light L22 passes through the short axis of liquidcrystal 515, the second group of light L22 loses a relatively smallquantity of light while passing through liquid crystal 515 compared withthe first group of light L21. Therefore, the first group of light L21 ofthe second light L2 has a quantity of light less than that of the secondgroup of light L22 of the second light L2.

The first group of light L21 is reflected by the first sidewall 563 a sothat the light path thereof is changed in parallel to the short axis ofliquid crystal 515. The second group of light L22 is reflected by thesecond sidewall 563 b so that the light path thereof is changed inparallel to the long axis of liquid crystal 515. On the other hand, thefront-side light L24-f, the left-side light L24-l and the right-sidelight L24-r of the fourth group of light L24 pass through the pores 565of the first porous film 560, without making contact with the firstporous film 560.

Accordingly, the first group of light L21 compensates for luminance ofthe left-side light L24-l tilted in a left direction with respect to thesecond direction D2, to thereby exit light having uniform luminance. Inaddition, the second group of light L22 compensates for luminance of theright-side light L24-r tilted in a right direction with respect to thesecond direction D2, to thereby exit light having uniform luminance.That is, the first porous film 560 allows the second light L2, whichrepresents different luminance characteristic depending on viewingpoints thereof, to be exited as third light L3 to provide expandedviewing angle. Therefore, the first porous film 560 expands the viewingangle of the liquid crystal display device 1000 and prevents the “grayscale inversion”, which occurs when the viewing angle exceeds apredetermined level.

In addition, since the porous film 560 allows the front-side light L24-fto directly pass through the pores 565, luminance of the liquid crystaldisplay device 1000 will be improved when viewed from a front of theliquid crystal display device 1000.

FIGS. 6A to 6E are views showing the plurality of pores formed in thefirst porous film.

Referring to FIG. 6A, the first porous film 560 includes a plurality ofplural pores 565 having a regular square shape. Since the pores 565 havethe regular square shape, front, rear, left, and right sidewalls (notshown) of the first porous film 560 have equal sectional area. Thus, thefirst porous film 560 can compensate for luminance in front, rear, left,and right directions of the pores 565.

On the other hand, referring to FIGS. 6B and 6C, the first porous film560 includes a plurality of plural pores 565 having a horizontallyelongated rectangular shape or a horizontally elongated oval shape.Since the pores 565 have the horizontally elongated rectangular shape orthe horizontally elongated oval shape, sectional areas of the front andrear sidewalls (not shown) of the first porous film 560 are larger thansectional areas of the left and right sidewalls of the first porous film560. Thus, the first porous film 560 can better compensate for luminancein the front and rear directions of the pores 565 compared with in theleft and right directions of the pores 565.

In addition, referring to FIGS. 6D and 6E, the first porous film 560includes a plurality of plural pores 565 having a vertically elongatedrectangular shape or a vertically elongated oval shape. Since the pores565 has the vertically elongated rectangular shape or the verticallyelongated oval shape, sectional areas of the left and right sidewalls(not shown) of the first porous film 560 are larger than sectional areasof the front and rear sidewalls of the first porous film 560. Thus, thefirst porous film 560 can better compensate for luminance in left andright directions of the pores 565 compared with in the front and leftdirections of the pores 565.

The present invention has been described with reference to the firstporous film 560 having a single layer structure. Hereinafter, thepresent invention will be described with reference to second and thirdporous films having multi-layer structure.

FIGS. 7A and 7B are views showing the second porous film according toanother exemplary embodiment of the present invention.

Referring to FIG. 7A and 7B, the second porous film 570 includes aporous layer 571 having a plurality of pores 571, and a supporting layer572 for supporting an incident surface 571 b of the second porous layer571. The supporting layer 572 is integrally formed with the secondporous layer 571.

The second porous layer 571 has the incident surface 571 discontinuouslyextended in the first direction D1 parallel to an upper surface of thesupporting layer 572, an exiting surface 571 c opposite to the incidentsurface 571, and a plurality of sidewalls 571 d connecting the incidentsurface 571 b to the exiting surface 571 c and extended in the seconddirection D2 perpendicular to the upper surface of the supporting layer572.

FIGS. 8A and 8B are views showing the third porous film according toanother exemplary embodiment of the present invention.

Referring to FIG. 8A and 8B, the third porous film 580 includes a porouslayer 581 having a plurality of pores 581, a first supporting layer 582for supporting an incident surface 581 b of the third porous layer 581,and a second supporting layer 583 for supporting an exiting surface 581c of the porous layer 581. The first and second supporting layers 582and 583 are integrally formed with the porous layer 581.

The third porous layer 581 has the incident surface 581 adiscontinuously extended in the first direction D1 parallel to uppersurfaces of the first and second supporting layers 582 and 583, theexiting surface 581 c opposite to the incident surface 581, and aplurality of sidewalls 581 d connecting the incident surface 581 b tothe exiting surface 581 c and extended in the second direction D2perpendicular to the upper surfaces of the first and second supportinglayers 582 and 583.

Hereinafter, a second embodiment of the present invention will bedescribed, in which the first, second and third porous films 560, 570and 580 are not provided in the liquid crystal display device 1000 asseparate elements, but integrally formed with a polarizing plate, whichis installed at an upper or a lower portion of the liquid crystaldisplay panel 510 to perform a polarizing function.

FIGS. 9 and 10 are views showing a structure of the polarizing plate ofthe liquid crystal display device according to the exemplary secondembodiment of the present invention.

Referring to FIG. 9, a first polarizing plate 590 includes a polarizinglayer 591 for outputting third light (not shown) by polarizing secondlight (not shown), which is exited from the liquid crystal panel 510 andincludes image information, a supporting layer 592 disposed between thepolarizing layer 591 and the liquid crystal display device 510 so as tosupport the polarizing layer 591, and a porous layer 593 having aplurality of pores and being disposed on the polarizing layer 591 so asto output fourth light (not shown) providing an expanded viewing angleby partially changing a path of the third light polarized by thepolarizing layer 591.

Generally, the polarizing layer 591 is formed by absorbing iodine ordichromatic dyes into polyvinyl alcohol (PVA) layer, which is extendedin a third direction parallel to the upper surface of the liquid crystaldisplay panel 510.

Since iodine molecules and dye molecules have dichromatic property, theyabsorb the light vibrating in parallel to the third direction andtransmit the light vibrating perpendicular to the third direction.Accordingly, the polarizing layer 591 absorbs light components vibratingin the third direction and transmits light components vibrating in afourth direction, which is parallel to the upper surface of the liquidcrystal display panel 510 and perpendicular to the third direction.

The supporting layer 592 is comprised of triacetate cellulose(hereinafter, referred to TAC) resin having a superior endurance, andsupports and protects the polarizing layer 591.

The porous layer 593 has an incident surface 593 b discontinuouslyextended in the first direction D1 parallel to an upper surface of thepolarizing layer 591, an exiting surface 593 c opposite to the incidentsurface 593 b, and a plurality of sidewalls 593 d connecting theincident surface 593 b to the exiting surface 593 c and extended in thesecond direction D2 perpendicular to the upper surface of the polarizinglayer 591. Accordingly, the porous layer 593 outputs fourth light toprovide expanded viewing angle by partially changing the path of thethird light exited from the polarizing layer 591 through the sidewall593 d.

The porous layer 593, like the supporting layer 592, includes TAC resinhaving a superior endurance, and supports and protects the polarizinglayer 591.

Referring to FIG. 10, a second polarizing plate 595 includes a porouslayer 596, a polarizing layer 597 and a supporting layer 598. The porouslayer 596 has a plurality of pores and outputs third light (not shown)to provide expanded viewing angle by partially changing a path of secondlight (not shown) exited from the liquid crystal display panel 510. Thepolarizing layer 597 is disposed on the porous layer 596 to polarize thethird light. The supporting layer 598 is disposed on the polarizinglayer 597 and supports the polarizing layer 597.

The porous layer 596 has an incident surface 596 b discontinuouslyextended in the first direction D1 parallel to an upper surface of thepolarizing layer 597, an exiting surface 596 c opposite to the incidentsurface 596 b, and a plurality of sidewalls 596 d connecting theincident surface 596 b to the exiting surface 596 c and extended in thesecond direction D2 perpendicular to the upper surface of the polarizinglayer 597.

Accordingly, the porous layer 596 outputs third light to provideexpanded viewing angle by partially changing the path of a polarizedsecond light exited from the liquid crystal display panel 510 throughthe sidewall 596 d.

<Simulation of Gray Scale Inversion According to Variation of ViewingAngles>

Hereinafter, a first porous film having a plurality of pores with a sizeabout 5 μm is used in sample 1 so as to measure luminance of the liquidcrystal display device, and a first porous film having a plurality ofpores with a size about 2 μm is used in sample 2 so as to measureluminance of the liquid crystal display device. In addition, the firstporous film is not used in comparative sample 1.

FIGS. 11A to 11C are graphs showing luminance variation according toviewing angles obtained by using comparative sample 1, FIGS. 12A to 12Care graphs showing luminance variation according to viewing anglesobtained by using sample 1, and FIGS. 13A to 13C are graphs showingluminance variation according to viewing angles obtained by using sample2. Each curve of each graph shown in FIGS. 11A to 13C represents one of8-gray scales made by dividing 64-gray scales into 8-gray scales.

In detail, FIGS. 11A, 12A and 13A represent luminance variationdepending on viewing angles varying along a upper and lower direction ofa screen of the liquid crystal display panel. FIGS. 11B, 12B and 13B areenlarged views showing luminance variation at upper portions of thecurves in FIGS. 11A, 12A and 13A, respectively. FIGS. 11C, 12C and 13Care enlarged views showing luminance variation at lower portions of thecurves in FIGS. 11A, 12A and 13A, respectively. In FIGS. 11A to 13C, anx-axis represents a viewing angle (°) and a y-axis represents luminance(cd/m²).

Referring to FIGS. 11A to 11C, luminance does not increase although eachgray scale becomes higher, when the first porous film is not used. Inaddition, a lower gray scale has luminance higher than luminance of ahigher gray scale. That is, the “gray scale inversion” occurs at upperand lower portions when the viewing angles are about 24° and −44°,respectively.

On the contrary, referring to FIGS. 12A to 12C, when the first poroushaving a plurality of pores with a size about 5 μm is used, asatisfactory viewing angle characteristic can be achieved. That is,luminance increases according as each gray scale becomes higher. Indetail, the “gray scale inversion” just occurs at the upper portion ofthe curve only when the viewing angle is about 28°, the “gray scaleinversion” does not occur at the lower portion of the curve. Inaddition, the gray scale inversion is reduced in FIGS. 12A to 12C usingsample 1 compared with in FIGS. 11A to 11C using comparative sample 1.

In addition, referring to FIGS. 13A to 13C, when the first porous havinga plurality of pores with a size about 2 μm is used, a satisfactoryviewing angle characteristic can be achieved. That is, luminanceincreases according as each gray scale becomes higher. In detail, the“gray scale inversion” does not occur at the upper portion of the curveup to the viewing angle of about 80°. In addition, the “gray scaleinversion” does not occur at the lower portion of the curve down to theviewing angle of −80°. Thus, the gray scale inversion is reduced inFIGS. 13A to 13C using sample 2 compared with in FIGS. 11A to 11C usingcomparative sample 1.

FIG. 14 is an exploded perspective view showing a liquid crystal displaydevice according to an exemplary third embodiment of the presentinvention and FIG. 15 is a sectional view showing a liquid crystaldisplay device shown in FIG. 14.

Referring to FIGS. 14 and 15, the liquid crystal display device 1100according to the exemplary third embodiment of the present inventionincludes a backlight unit 600 for generating first light, and a displayunit 900 for displaying images.

The display unit 900 has a liquid crystal display panel 910 fordisplaying images, a lower polarizing plate 970 disposed below theliquid crystal display panel 910, an upper polarizing plate 980 disposedabove the liquid crystal display panel 910, and a porous film 960disposed on the upper polarizing panel 980.

The liquid crystal display panel 910 includes a TFT substrate 912, acolor filter substrate 914 and liquid crystal (not shown). The TFTsubstrate 912 includes TFTs (not shown), pixel electrodes (not shown)and a first alignment layer (not shown). The color filter substrate 914is opposite to the TFT substrate 912, and has color filters (not shown),common electrode (not shown) and a second alignment layer (not shown).Liquid crystal is disposed between the TFT substrate 912 and the colorfilter substrate 914. TN liquid crystal, in which a long axis of liquidcrystal is continuously twisted at a right angle from the pixelelectrode towards the common electrode, is mainly employed in the liquidcrystal display device.

The lower polarizing plate 970 polarizes first light incident from thebacklight unit 600, and provides the polarized first light to the liquidcrystal display panel 910. The polarized first light is incident intothe liquid crystal display panel 910, and is deflected in apredetermined direction while passing through the twisted liquidcrystal, which has an varied aligning angle depending on an electricfield applied to the liquid crystal, so that second light having imageinformation is outputted.

The second light is incident into the upper polarizing plate 980. Theupper polarizing plate 980 adjusts quantity of the second light, andimproves viewing angle of the second light.

FIG. 16 is a schematic view showing the display unit shown in FIG. 14,in detail.

Referring to FIG. 16, the TFT substrate 912 includes a plurality of gatelines 912 a extended in a column direction thereof (hereinafter,referred to a first direction D1), and a plurality of data lines 912 bextended in a row direction thereof (hereinafter, referred to a seconddirection D2). In addition, a plurality of TFTs 912 c is arranged on theTFT substrate 912 in a matrix shape. Source electrodes of the TFTs 912 care connected to the data lines 912 b, and gate electrodes of the TFTs912 c are connected to the gate lines 912 a. Drain electrodes of theTFTs 912 c are connected to pixel electrodes 912 d.

A first alignment layer 913 is deposited on an entire surface of the TFTsubstrate 912 having TFTs 912 c and pixel electrode 912 d. The firstalignment layer 913 includes a polyimid based organic layer and a firstrubbing pattern (not shown) formed on the polyimid based organic layerand rubbed in the first direction D1.

For example, the first rubbing pattern is extended precisely the samedirection as the first direction D1 in FIG. 16, but the first rubbingpattern can be extended in a tilted direction with respect to the firstdirection D1 by a predetermined angle. The predetermined angle isdetermined within a predetermined range, such that the extendeddirection of the first rubbing pattern does not extremely obviate fromthe first direction D1.

In addition, the color filter substrate 914 is disposed opposite to theTFT substrate 912. The color filter substrate 914 has color filters (notshown), common electrode (not shown) and a second alignment layer 915.Similar to the first alignment layer 913, the second alignment layer 915includes a polyimid based organic layer and a second rubbing pattern(not shown), the second rubbing pattern is formed on the polyimid basedorganic layer, and is rubbed in the second direction D2.

As shown in FIG. 16, if the first rubbing patterns extended in the firstdirection D1 are formed in the first alignment layer 913, and the secondrubbing patterns extended in the second directions D2 are formed in thesecond alignment layer 915, a process for rubbing the first and secondrubbing patterns can be simplified. In other words, when the first andsecond rubbing patterns are extended in the first and second directions(D1, D2), respectively, the distance of the rubbing process becomesshorter compared when the first and second rubbing patterns are extendedin a diagonal direction of a screen of the liquid crystal displaydevice, so that the rubbing process with respect to the first and secondalignment layers 913 and 915 can be simplified.

A liquid crystal layer 916 is disposed between the TFT substrate 912 andthe color filter substrate 914.

In addition, the lower polarizing plate 970 is disposed below the TFTsubstrate 912, and the upper polarizing plate 980 is disposed above thecolor filter substrate 914.

The lower polarizing plate 970 includes a first polarizing layer 971 andfirst and second supporting layers 972 and 973. The first and secondsupporting layers 972 and 973 are disposed at a upper and lower surfacesof the first polarizing layer 971 so as to support the first polarizinglayer 971. The first polarizing layer 971 polarizes incident light byabsorbing light components vibrating in the first direction D1 and bytransmitting light components vibrating in the second direction D2perpendicular to the first direction D1.

The upper polarizing plate 980 includes a second polarizing layer 981and third and fourth supporting layers 982 and 983. The third and fourthsupporting layers 982 and 983 is disposed at a upper an lower surfacesof the second polarizing layer 981 so as to support the secondpolarizing layer 981. The second polarizing layer 981 polarizes incidentlight by absorbing light components vibrating in the second direction D2and by transmitting light components vibrating in the first directionD1.

A first transmission axis extended in the first direction D1 is formedin the first polarizing layer 971, and a second transmission axisextended in the second direction D2 is formed in the second polarizinglayer 981, so that cutting errors, which occur during cutting the firstand second polarizing layers 971 and 981, can be prevented. Accordingly,productivity of the lower and upper polarizing plates 970 and 980 isimproved, and reduces cost for manufacturing of the lower and upperpolarizing plates 970 and 980.

Although not shown in FIG. 16, a first and second compensating films forcompensating for the viewing angle of the liquid crystal display device1100 can be disposed at the lower and upper polarizing plates 970 and980, respectively. Preferably, a direction of rubbing discotic liquidcrystal formed in the first compensating film is parallel to the firstdirection D1, and a direction of rubbing the discotic liquid crystalformed in the second compensating film is parallel to the seconddirection D2.

As shown FIG. 16, the first rubbing pattern is extended in the firstdirection D1, and the second rubbing pattern is extended in the seconddirection D2, but the present invention does not limited to thesestructures. Specifically, on the consumption that the first rubbingpattern is aligned perpendicular to the second rubbing pattern, each ofthe first and second rubbing patterns can be extended in an upper,lower, left and right directions with respect to a front of the screenof the liquid crystal display device. The directions of the first andsecond transmission axes formed in the first and second polarizingplates 970 and 980 vary in correspondence with the variations of thefirst and second rubbing patterns.

Referring to FIGS. 14 to 16, the porous film 960 having a sizecorresponding to a size of the liquid crystal display panel 910 isaligned on the liquid crystal display panel 910. The porous film 960includes a first incident surface 961 toward which second light exitedfrom the liquid crystal display device 910 is incident, an exitingsurface 962 for outputting second light, and sidewalls 963 connectingthe first incident surface 961 to the exiting surface 962. A pluralityof pores 965 extended from the incident surface 961 to the exitingsurface 962 are formed in the porous film 960.

Accordingly, the porous film 960 includes a plurality of sidewalls 964.The sidewalls 964 connect the incident surface 961 to the exitingsurface 962, and define the pores 965. The sidewalls change the path ofthe second light, thereby outputting third light to provide expandedviewing angle.

FIG. 17 is a schematic view showing viewing angle characteristicaccording to rubbing directions of first and second alignment layersshown in FIG. 16, and FIG. 18 is a schematic view showing the light pathto be changed by the porous film. In FIG. 17, left and right sides withrespect to a front of the screen are marked as A and A′, respectively,and, upper and lower sides with respect to a front of the screen aremarked as B and B′, respectively.

Referring to FIG. 17, a first rubbing pattern rubbed in the rightdirection A′ is formed in the first alignment layer, and a secondrubbing pattern rubbed in the downward direction B′ is formed in thesecond alignment layer. The liquid crystal 916 adjacent to the firstsecond rubbing patterns is aligned along the first rubbing pattern to betilted in the right direction (A′), and the liquid crystal 916 adjacentto the second rubbing patterns is aligned along the second rubbingpattern to be tilted in the downward direction (B′). Points shown inFIG. 17 represent a tilted direction of the liquid crystal 916.

If the liquid crystal is tilted toward the right side A′, a user catcheslight passing through the long axis of liquid crystal 916 when the userwatch the screen from the right side A′ above the screen, and the usercatches light passing though the short axis of liquid crystal 916 whenthe user watch the screen from the left side B′ above the screen. Thelight passed through the long axis of liquid crystal 916 has a lessquantity of light compared with the light passed through the short axisof liquid crystal 916. Accordingly, luminance variation is generated inthe right and left directions A′ and A.

In order to compensate for the luminance variation, the porous film 960is provided to the liquid crystal display device 1100. Hereinafter, theluminance variation will be described in FIG. 18. Since lower and upperpolarizing plates are not illustrated in FIG. 18, they will not bedescribed below.

Referring to FIG. 18, the liquid crystal display panel 910 includes theTFT substrate 912, the color filter substrate 914 and liquid crystal916. The TFT substrate 912 has the TFTs 912 c, the pixel electrode 912 dand the first alignment layer 913. The color filter substrate 914 isopposite to the TFT substrate 912 and has color filters 914 a, commonelectrode 914 b and the second alignment layer 915. Liquid crystal 916is disposed between the TFT substrate 912 and the color filter substrate914.

When voltage is applied to both the pixel electrode 912 b and the commonelectrode 914 b, an electric field is formed between the pixel electrode912 b and the common electrode 914 b. Accordingly, an alignment angle ofliquid crystal 915 varies, and quantity of light incident into theliquid crystal display panel 910 is adjusted, to thereby output secondlight L2 having a predetermined quantity of light. Then, second light L2is incident into the porous film 960. According to FIG. 18, the secondlight L2 is incident into a first sidewall 964 a and reflected therebyat a predetermined angle. The first sidewall 964 a reflects a group ofsecond light L2 having a first incident angle larger than a criticalangle of the porous film 960.

The size of the pores 965 is preferably smaller than the size of a unitpixel formed on the TFT substrate 912. In addition, thickness t of theporous film 960 is preferably in a range about 5 to 100 μm.

As shown in FIG. 18, when the electric field is formed between the pixelelectrode 912 d and the common electrode 914 b, the long axis of liquidcrystal 916 is tilted by a predetermined angle with respect to the firstdirection D1. When the first light L1 is provided to the liquid crystaldisplay panel 910, the first light L1 has some quantity of lightadjusted by the tilted liquid crystal 916, so that the second light L2having image information is exited.

On the assumption that liquid crystal 916 is tilted in the firstdirection D1, the first group of light L21 reflected by the firstsidewall 964 a is outputted through the long axis of liquid crystal 916,and the second group of light L22 reflected by a second sidewall 964 bopposite to the first sidewall 964 a is outputted through the short axisof liquid crystal 916.

Since the first group of light L21 passes through the long axis ofliquid crystal 916, relatively large loss of light will be caused whilethe first group of light L21 passes through the liquid crystal 916. Onthe contrary, since the second group of light L22 passes through theshort axis of liquid crystal 916, relatively small loss of light will becaused while the second group of light L22 passes through liquid crystal916. Therefore, the first group of light L21 has a quantity of lightless than that of the second group of light L22.

The path of the first group of light L21 reflected by the first sidewall964 a is changed to proceed in a direction parallel to the long axis ofliquid crystal 916. In addition, the path of the second group of lightL22 reflected by the second sidewall 964 b is changed to proceed in adirection parallel to the short axis of liquid crystal 916. Accordingly,the luminance variation can be reduced at the left and right sides A andA′.

Referring again to FIGS. 17 and 18, the viewing angle of the liquidcrystal display device 1100 is expanded since the first and secondrubbing patterns 913 a and 915 a formed on the first and secondalignment layers 913 and 915 are rubbed in the first and seconddirections D1 and D2, respectively. In detail, left and right viewingangles of the liquid crystal display device 1100 are expanded accordingas luminance increases in a white mode of the liquid crystal displaydevice 1100. In addition, upper and lower viewing angles are improvedaccording as luminance decreases in a black mode of the liquid crystaldisplay device 1100.

According to the above principle, luminance can be increased in thewhite mod by providing the first and second rubbing patterns 913 a and915 a extended in the right and lower directions A′ and B′,respectively, in the liquid crystal display device 1100. In addition, itis possible to prevent light from being leaked in the black mode of theliquid crystal display device 1100, so that luminance is reduced in theblack mode. Thus, the left and right viewing angles and the upper andlower viewing angles of the liquid crystal display device 1100 can beexpanded.

FIGS. 19 and 21 are sectional views showing a liquid crystal displaydevice 1200 according to an exemplary fourth embodiment of the presentinvention, and FIG. 20 is a perspective view showing a display unit 900shown in FIG. 19.

Referring to FIG. 19, the liquid crystal display device 1200 includesthe display unit 900 for displaying images and a backlight unit 600 forgenerating light. The display unit 900 has a liquid crystal displaypanel 910, a lower polarizing plate 970 disposed below the liquidcrystal display panel 910, and an upper polarizing plate 990 disposedabove the liquid crystal display panel 910.

As shown in FIG. 20, the liquid crystal display panel 910 includes a TFTsubstrate 912, a color filter substrate 914 and liquid crystal 916disposed between the TFT substrate 912 and the color filter substrate914.

In detail, the TFT substrate 912 has a plurality of gate lines 912 aextended in the first direction, and a plurality of data lines 912 bextended in the second direction D2. In addition, a plurality of TFTs912 c is arranged on the TFT substrate 912 in a matrix shape. That is,source electrodes of the TFTs 912 c are connected to the data lines 912b, and gate electrodes of the TFTs 912 c are connected to the gate lines912 a. Drain electrodes of the TFTs 912 c are connected to pixelelectrodes 912 d. A first alignment layer 913 is deposited on an entiresurface of the TFT substrate 912 having the TFT 912 c and the pixelelectrode 912 d. An organic layer comprised of polyimid series materialis deposited on the first alignment layer 913, and then a first rubbingpattern (not shown) rubbed in the first direction D1 is formed on theorganic layer.

In addition, a color filter substrate 914 faces the TFT substrate 912.The color filter substrate 914 includes color filters (not shown),common electrode (not shown) and a second alignment layer 915. Similarto the first alignment layer 913, an organic layer comprised of polyimidseries material is deposited on the second alignment layer 915, and thena second rubbing pattern (not shown) rubbed in the second direction D2is formed on the organic layer.

The lower polarizing plate 970 is disposed between the TFT substrate 912and an optical sheet 630, and the upper polarizing plate 990 is disposedabove the color filter substrate 914.

The lower polarizing plate 970 includes a first polarizing layer 971 anda first and a second supporting layers 972 and 973. The first polarizinglayer 971 polarizes light. The first and second supporting layers 972and 973 is disposed on an upper a lower surfaces of the first polarizinglayer 971 so as to support the first polarizing layer 971.

The first polarizing layer 971 is formed by adsorbing iodine ordichromatic dyes onto a PVA layer, the PVA layer has a transmission axisextended in the first direction D1.

The upper polarizing plate 990 includes a second polarizing layer 991for polarizing light, a third supporting layer 992 disposed on a lowersurface of the second polarizing layer 991, and a porous layer 993disposed on an upper surface of the second polarizing layer 991. Theporous layer 993 has a plurality of pores 993 a. The porous layer 993includes sidewalls 993 b, each sidewall 993 b is defined by each pore993 a. The sidewalls 993 b partially change the path of the lightincident into the upper polarizing plate 990, thereby exiting light toprovide expanded viewing angle.

As mentioned above, since the upper polarizing plate 990 has the porouslayer 993 on the second polarizing layer 991, the upper polarizing plate990 polarizes third light and improves the viewing angle of a polarizedthird light. On the other hand, the porous layer 993 can be formed onthe lower surface of the second polarizing layer 991, which will bedescribed later with reference to FIG. 21.

Although it is illustrated that the first rubbing pattern is extended inthe first direction D1 and the second rubbing pattern is extended in thesecond direction D2, the present invention does not limited to thesestructures. In detail, on the assumption that the first rubbing patternis aligned perpendicular to the second rubbing pattern, each of thefirst and second rubbing patterns can be extended in upper, lower, leftor right directions when viewed from a front of the screen of the liquidcrystal display device. Directions of the first and second transmissionaxes formed in the first and second polarizing layers 971 and 991 varyaccording as directions of the first and second rubbing patterns vary.

Referring to FIG. 21, an upper polarizing plate 995 aligned above thecolor filter substrate 914 includes a second polarizing layer 996 forpolarizing light, a porous layer 998 formed on a lower surface of thesecond polarizing layer 996, and a third supporting layer 997 formed onan upper surface of the second polarizing layer 996.

Since the porous layer 998 is disposed on the lower surface of thesecond polarizing layer 996, the third light exited from the liquidcrystal display device 910 provide expanded viewing angle, thenpolarized by the second polarizing layer 996 to output fourth light.

Hereinafter, gray scale inversion characteristic according to variationof viewing angles of the liquid crystal display device 1100 having theporous film 960 will be described in detail with reference to simulationresults.

FIGS. 22A to 22C are graphs showing simulation results obtained throughexperiment 1 according to the present invention, and FIGS. 23A to 23Care graphs showing simulation results obtained through experiment 2according to the present invention. In Experiments 1 and 2, the liquidcrystal display device has a porous layer, and a first and secondalignment layers having a first and a second rubbing patterns rubbed ina vertical or a horizontal direction. In detail, in experiment 1, theporous film has a thickness of about 11 μm, and each pore formed in theporous film has a diameter of about 5 μm. In addition, in experiment 2,the porous film has a thickness of about 18 μm, and each pore formed inthe porous film has a diameter of about 1 μm.

FIGS. 24A to 24C are graphs showing simulation results obtained throughcomparative experiment 1, and FIGS. 25A to 25C are graphs showingsimulation results obtained through comparative experiment 2. In thecomparative experiment 1, rubbing patterns rubbed in a diagonaldirection are formed on the first and second alignment layers. Incomparative experiment 2, rubbing patterns rubbed in vertical andhorizontal directions are formed on the first and second alignmentlayers.

In FIGS. 22A, 23A, 24A, and 25A, an X-axis represents a viewing angle,and a Y-axis represents a contrast ratio. In addition, when viewing thescreen of the liquid crystal display device 1100 from a front thereof, avertical direction is defined as a direction extended from an upperportion to a lower portion of the screen, and a horizontal direction isdefined as a direction extended from a left side to a right side of thescreen. In the FIGS. 22A, 23A, 24A, and 25A, a bold solid linerepresents the contrast ratio according to variation of viewing angleswhen viewing the screen along the vertical direction. In addition, athin solid line represents the contrast ratio according to variation ofviewing angles when viewing the screen along the horizontal direction.

On the other hand, in FIGS. 22B, 22C, 23B, 23C, 24B, 24C, 25B and 25C,an X-axis represents a viewing angle (°), and a Y-axis representsluminance (cd/m²). In detail, FIGS. 22B, 23B, 24B, and 25B showluminance variation according to variation of viewing angles whenviewing the screen along the horizontal direction. FIGS. 22C, 23C, 24C,and 25C show variation of luminance according to variation of viewingangles when viewing the screen along the vertical direction. Each curveof each graph shown in FIGS. 22B to 25C represents one of 8-gray scalesmade by dividing 64-gray scales into 8-gray scales.

Referring to FIGS. 24A and 25A, the contrast ratio varies depending onthe viewing angle. That is, the contrast ratio is the highest at thefront of the screen and greatly decreases according as the distancebetween the front of the screen and an observation point increase.Especially, the contrast ratio greatly decreases according as thedistance between the front of the screen and the observation pointincreases along the vertical and horizontal directions. A distributionof the contrast ratio is asymmetric depending on the vertical directionor the horizontal direction.

As a result, the contrast ratio can be varied depending on eachdirection. Namely, the contrast ratio can be varied depending on thedirection from which a user watches the screen.

Referring to FIGS. 22A and 23A, the contrast ratio according to theviewing angles is substantially constant, especially the contrast ratiois hardly varied when viewing the screen along the vertical andhorizontal direction. Especially, since the size of pores used inexperiment 2 is smaller than the size of pores used in experiment 1, thecontrast ratio is more uniform in experiment 2 than in experiment 1.

As shown in FIGS. 24B, when viewing the screen along the horizontaldirection, the gray scale inversion does not occur and the asymmetricdistribution of the contrast ratio is not created. However, as shown inFIGS. 24C, when viewing the screen along the vertical direction, thegray scale inversion occurs. Especially, as shown in FIGS. 24C, whenviewing the screen along the vertical direction, the gray scaleinversion occurs at an upper portion of the curves where the viewingangel is about 24° and at a lower portion of the curves where theviewing angel is about −44°. Accordingly, the viewing angle of theliquid crystal display device is limited.

In addition, referring to FIGS. 25B and 25C, when viewing the screenalong the vertical direction, the viewing angle is expanded comparedwith a comparative experiment. That is, the gray scale inversion isreduced when viewing the screen along the vertical direction. However,as shown in FIG. 25B, luminance variation is generated between the leftand right portions of the graph. That is, the asymmetric distribution ofthe luminance is generated between the left and right portions of thegraph.

However, referring to FIGS. 22B, 22C, 23B and 23C, luminance increasesaccording as each gray scale becomes higher even when the distancebetween the front of the screen and the observation point increase.Thus, the viewing angle of the liquid crystal display device can beexpanded. In addition, as shown in FIGS. 22B and 23B, luminance issymmetrically distributed between the left and right portions of thegraph.

While the present invention has been described in detail with referenceto the preferred embodiments thereof, it should be understood to thoseskilled in the art that various changes, substitutions and alterationscan be made hereto without departing from the scope of the invention asdefined by the appended claims.

Industrial Applicability

According to the liquid crystal display device of the present invention,a porous film has sidewalls defined by a plurality of pores. Thesidewalls of the porous film reflect a first group of light of thesecond light. The second light is exited from a liquid crystal displaypanel, and the first group of light is light passes through a short axisof liquid crystal. The first group of light is reflected towards asecond group of light of the second light, which passes through a longaxis of liquid crystal. Since the first group of light having relativelyhigher luminance is reflected towards the second group of light havingrelatively lower luminance, a viewing angle is expanded in such a mannerthat a person can precisely recognize image information displayed in ascreen of the liquid crystal display panel from all directions withrespect to the screen.

In addition, a lower substrate includes a first alignment layer having afirst rubbing pattern extended in a column or row direction, and anupper substrate includes a second alignment layer having a secondrubbing pattern extended in a lo row or column direction. Thus, theviewing angle in an upper and lower portions of the screen can beimproved due to the rubbing direction of the first and second rubbingpatterns.

Furthermore, since the rubbing pattern is formed on the alignment layerin the column or row direction, a length of the rubbing can be shortenedwhen rubbing the alignment layer. Accordingly, the manufacturing processfor the liquid crystal display device can be simplified and themanufacturing cost thereof can be saved.

1. A liquid crystal display device comprising: a liquid crystal displaypanel for receiving a first light, and for radiating a second lighthaving an image information, the liquid crystal display panel including:i) a first substrate on which a plurality of pixels having a firstelectrode is formed, ii) a second substrate on which a second electrodeopposite to the first electrode is formed, and iii) a liquid crystallayer, disposed between the first and second substrate, which is alignedby an electric field applied between the first and second electrodes;and a light path changing means disposed on the liquid crystal displaypanel, the light path changing means including a reflection surface, thereflection surface reflecting a part of the second light and outputtinga third light having a compensated luminance, and the reflection surfacebeing extended in a first direction perpendicular to an upper surface ofthe liquid crystal display panel, wherein the light path changing meansincludes a porous film having a plurality of pores.
 2. The liquidcrystal display device as claimed in claim 1, wherein the liquid crystalincludes nematic liquid crystal.
 3. The liquid crystal display device asclaimed in claim 1, wherein the reflection surface includes innersidewalls of the porous film, and each of the inner sidewalls isadjacent to each of the pores.
 4. The liquid crystal display device asclaimed in claim 1, wherein the porous film has a refractive indexlarger than the pores.
 5. The liquid crystal display device as claimedin claim 1, wherein each of the pores is smaller than the pixels.
 6. Theliquid crystal display device as claimed in claim 1, wherein the lightpath changing means has a multi-layered structure.
 7. The liquid crystaldisplay device as claimed in claim 6, wherein the light path changingmeans further includes a supporting layer, the supporting layer beingextended in a second direction to fully cover an incident surface of theporous film, the second light being incident through the incidentsurface.
 8. The liquid crystal display device as claimed in claim 6,wherein the light path changing means further includes a firstsupporting layer extended in a second direction to fully cover anincident surface of the porous film, the second light being incidentthrough the incident surface, and a second supporting layer extended inthe second direction to fully cover an exiting surface of the porousfilm, the third light being exited through the exiting surface.
 9. Aliquid crystal display device comprising: a liquid crystal display panelfor receiving a first light, and for radiating a second light having animage information, the liquid crystal display panel including: i) afirst substrate on which a plurality of pixels having a first electrodeis formed, ii) a second substrate on which a second electrode oppositeto the first electrode is formed, and iii) a liquid crystal layer,disposed between the first and second substrate, which is aligned by anelectric field applied between the first and second electrodes; and apolarizing plate disposed on the liquid crystal display panel, thepolarizing plate including: i) a polarizing layer for polarizing thesecond light, and ii) a light path changing layer including a reflectionsurface, the reflection surface for reflecting a part of the secondlight and outputting a third light having a compensated luminance, thereflection surface extended in a first direction perpendicular to anupper surface of the liquid crystal display panel, wherein the lightpath changing layer includes a plurality of pores.
 10. The liquidcrystal display device as claimed in claim 9, wherein the light pathchanging layer is disposed on the polarizing layer.
 11. The liquidcrystal display device as claimed in claim 10, wherein the reflectionsurface includes inner sidewalls of the light path changing layer, eachof the inner sidewalls being adjacent to each of the pores.
 12. Theliquid crystal display device as claimed in claim 11, wherein the lightpath changing layer has a refractive index larger than the pores. 13.The liquid crystal display device as claimed in claim 11, wherein eachof the pores is smaller than the pixels.
 14. A liquid crystal displaydevice comprising: a liquid crystal display panel for receiving a firstlight, and for radiating a second light having an image information, theliquid crystal display panel including: i) a first substrate on which aplurality of pixels having a first electrode is formed, ii) a secondsubstrate on which a second electrode opposite to the first electrode isformed, and iii) a nematic liquid crystal, disposed between the firstand second substrate, which is aligned by an electric field appliedbetween the first and second electrodes; and a light path changing meansdisposed on the liquid crystal display panel, the light path changingmeans including a reflection surface, the reflection surface reflectinga part of a first group of the second light towards a second group ofthe second light, the first group of light of the second light passingthrough the nematic liquid crystal in a parallel direction with regardto a first axis of the nematic liquid crystal tilted at a predeterminedangle by the electric field, the second group of light of the secondlight passing through the nematic liquid crystal in a parallel directionwith regard to a second axis of nematic liquid crystal, and the secondaxis being perpendicular to the first axis of nematic liquid crystal,wherein the light path changing means includes a porous film having aplurality of pores.
 15. The liquid crystal display device as claimed inclaim 14, wherein the first group of the second light has a luminancehigher than the second group of the second light.
 16. The liquid crystaldisplay device as claimed in claim 14, wherein the reflection surfaceincludes inner sidewalls, each of the inner sidewalls being adjacent toeach of the pores.
 17. The liquid crystal display device as claimed inclaim 14, wherein each pore has a size smaller than a size of eachpixel.
 18. The liquid crystal display device as claimed in claim 14,wherein the porous film has a refractive index larger than a refractiveindex of pores.
 19. A liquid crystal display device comprising: a liquidcrystal display panel for receiving a first light, and for radiating asecond light having an image information, the liquid crystal displaypanel including: i) a first substrate on which a plurality of pixelshaving a first electrode is formed, ii) a second substrate on which asecond electrode opposite to the first electrode is formed, and iii) anematic liquid crystal, disposed between the first and second substrate,for being aligned by an electric field applied between the first andsecond electrodes; and a polarizing plate disposed on the liquid crystaldisplay panel, the polarizing plate including: i) a polarizing layer forpolarizing the second light, and ii) a light path changing layerincluding a reflection surface, the reflection surface having aplurality of pores and inner sidewalls adjacent to each of the pores,the inner sidewalls reflecting a part of a first group of light of thesecond light towards a second group of light of the second light, thefirst group of light of the second light passing through the nematicliquid crystal in a parallel direction with regard to a first axis ofthe nematic liquid crystal tilted at a predetermined angle by theelectric field, the second group of light of the second light passingthrough the nematic liquid crystal in a parallel direction with regardto a second axis of nematic liquid crystal, and the second axis beingperpendicular to the first axis of nematic liquid crystal.
 20. Theliquid crystal display device as claimed in claim 19, wherein the firstgroup of light of the second light has luminance higher than luminanceof the first group of light.
 21. The liquid crystal display device asclaimed in claim 20, wherein the light path changing layer is disposedon the polarizing layer.
 22. A liquid crystal display device comprising:a lower substrate including: i) a plurality of switching devicesarranged in a matrix shape on a first substrate, ii) a first electrodeelectrically coupled to the switching devices, and iii) a firstalignment layer deposited on the first substrate and having a firstrubbing pattern extended in a first direction; an upper substrateincluding: i) a color filter formed on a second substrate, ii) a secondelectrode formed on the color filter, and iii) a second alignment layerdeposited on the second electrode and having a second rubbing patternextended in a second direction; a liquid crystal layer disposed betweenthe upper and lower substrates; and a light path changing meansincluding a plurality of pores and sidewalls being defined by the pores,the light path changing means disposed on the upper substrate andreflecting a part of a first light to output a second light having acompensated luminance distribution, the first light exited from theupper substrate and being incident into sidewalls of the light pathchanging means.
 23. The liquid crystal display device as claimed inclaim 22, further comprising: a backlight assembly, disposed below thelower substrate, for generating a third light; a first polarizing means,disposed between the lower substrate and the backlight assembly, forpolarizing the third light; and a second polarizing means, disposedbetween the upper substrate and the light path changing means, forpolarizing the first light.
 24. The liquid crystal display device asclaimed in claim 23, wherein the first polarizing means includes a firstpolarizing layer having a first transmission axis parallel to the seconddirection, and the second polarizing means includes a second polarizinglayer having a second transmission axis parallel to the first direction.25. The liquid crystal display device as claimed in claim 22, whereinthe light path changing means includes a porous film having a pluralityof pores.
 26. A liquid crystal display device comprising: a lowersubstrate including: i) a plurality of switching devices arranged in amatrix shape on a first substrate, ii) a first electrode electricallycoupled to the switching devices, and iii) a first alignment layerdeposited on the first substrate and having a first rubbing patternextended in a first direction; an upper substrate including: i) a colorfilter formed on a second substrate, ii) a second electrode formed onthe color filter, and iii) a second alignment layer deposited on thesecond electrode and having a second rubbing pattern extended in asecond direction; a liquid crystal layer disposed between the upper andlower substrates; a first polarizing means, disposed on a lower surfaceof the lower substrate, for polarizing a first light incident into thelower substrate; and a second polarizing means, disposed on the uppersubstrate, for polarizing a second light exited from the uppersubstrate, and for reflecting a part of second light to output a thirdlight having a compensated luminance, and wherein the second polarizingmeans includes a porous layer having a plurality of pores.
 27. Theliquid crystal display device as claimed in claim 26, wherein the firstpolarizing means includes a first polarizing layer having a firsttransmission axis parallel to the second direction, and the secondpolarizing means includes a second polarizing layer having a secondtransmission axis parallel to the first direction.
 28. The liquidcrystal display device as claimed in claim 27, wherein the porous layerhas sidewalls defined by the pores, the second polarizing means isdisposed on the second polarizing layer, the porous layer reflects apart of the second light to output a third light having a compensatedluminance distribution, and the second light is polarized by the secondpolarizing layer and is incident into the sidewalls of the light pathchanging means.